1. Field of the Invention
This invention relates to a metallized film suited as a wrapping film.
2. Description of the Related Art
Since plastic films have good mechanical properties and are highly planar, they are metallized and used as wrapping films.
However, the conventional metallized film used for wrapping have drawbacks in that the adhesion between the metallic layer and the base plastic film is weak, so that the portions of the metallic layer may be embossed or peeled off due to abrasion. Further, because the metallic layer is not well adhered to the plastic base film, the metallic film may be peeled off due to the blocking at high temperature and high humidity (in summer time) and the metallic luster of the metallic layer may become dull. Still further, since the conventional metallized wrapping films do not prevent the permeation of water vapor and/or oxygen very well, if they are used as wrapping films for crispy foods such as potato chips, crackers and rice crackers, the foods become humid and/or turn bad because of oxidation in a comparatively short time.
To overcome these problems, some proposals have been made and described in, for example, Japanese Laid-open Patent Application (Kokai) No. 47-29463 and Japanese Patent Publication (Kokoku) Nos. 63-54541 and 2-41344. However, even in these improved metallized films, the adhesion between the metallic layer and the base plastic film is not sufficient or the process for promoting the adhesion is complicated, or the prevention of permeation of water vapor and/or oxygen is not sufficient.
On the other hand, metallized films for metallized capacitors in which aluminum and other elements are deposited are disclosed in Japanese Laid-open Patent Application (Kokai) Nos. 53-81941, 53-85365 and 55-105319. However, since the metallized films are for capacitors, the permeability of water vapor and oxygen of these films are not mentioned at all, and, needless to say, they have no suitable heat-sealing layer so that they are not suitable as wrapping films.